Stdlib: fix signature of Reader.forEachLine() function

#KT-4242 Fixed

libraries/stdlib/src/kotlin/io/JIO.kt

@@ -211,17 +211,10 @@ public fun Writer.buffered(bufferSize: Int = defaultBufferSize): BufferedWriter
 /**
  * Iterates through each line of this reader then closing the [[Reader]] when its completed
  */
-public inline fun Reader.forEachLine(block: (String) -> Any): Unit {
+public inline fun Reader.forEachLine(block: (String) -> Unit): Unit = useLines { lines -> lines.forEach(block) }
-    this.use{
-        val iter = buffered().lineIterator()
-        while (iter.hasNext()) {
-            val elem = iter.next()
-            block(elem)
-        }
-    }
-}
 
-public inline fun <T> Reader.useLines(block: (Iterator<String>) -> T): T = this.buffered().use<BufferedReader, T>{block(it.lineIterator())}
+public inline fun <T> Reader.useLines(block: (Iterator<String>) -> T): T =
+        this.buffered().use<BufferedReader, T>{ block(it.lineIterator()) }
 
 /**
  * Returns an iterator over each line.

libraries/stdlib/test/IoTest.kt

@@ -52,7 +52,6 @@ class IoTest(){
 
     test fun testForEachLine() {
         val list = ArrayList<String>()
-        val reader = sample()
 
         /* TODO would be nicer maybe to write this as
             reader.lines.forEach { ... }
@@ -65,11 +64,18 @@ class IoTest(){
 
           if thing is not an Iterable/array/Iterator but has a suitable forEach method
         */
-        reader.forEachLine{
+        sample().forEachLine {
             list.add(it)
         }
 
         assertEquals(arrayListOf("Hello", "World"), list)
+
+        var count = 0
+        sample().forEachLine {
+            count += 1
+        }
+
+        assertEquals(2, count)
     }
 
     test fun testForEachLineFile() {